This invention relates to an apparatus for the removal of deposits on the internal walls of closed reactor vessels, the deposits are on the walls, above the level of a liquid reaction mixture, which is agitated by an agitator.
Chemical syntheses are frequently conducted in closed reaction vessels in order to avoid any contamination from outside sources as much as possible. Thus, for example, catalyzed processes are frequently conducted with the exclusion of air, and microbiological processes are conducted under sterile conditions. In the latter case, the substrate is reacted in a suitable reactor with the microorganisms under otherwise sterile conditions. In many cases, air is introduced to a certain extent in conducting the reaction under agitation. Because of substances present in the nutrient solution or substances formed by metabolic processes, the reaction mixture foams to some degree. The foam carrying microorganisms and substances out of the liquid deposits above the level of the reaction mixture on the inner walls and also on the inner surface of the lid of the reactor. The use of defoaming agents to avoid the foaming is not usually feasible because the defoamers are not suitable to be used in some cases and in most cases they exert a negative effect on the microbiological reactions. The deposits on the walls of the reactor above the liquid level make it almost impossible to conduct the process with precision, and thus in a reproducible manner, the reason being that the reaction which takes place in the deposited substance does not proceed similarly as it does in the reaction mixture. Thus, the samples withdrawn from the reaction mixture for analytical determination purposes do not take into account the deposits.
The mechanical removal of the foam, for example by the use of a scraper through the reactor lid, presents problems insofar as the sealing of the reaction vessel is concerned and thereby, for example, the sterility of the reaction mixture cannot be preserved.
A conventional device for preventing the deposits comprises the addition of a rinsing liquid. In practice, peepholes are provided to determine the formation of the deposits, but this procedure has the disadvantage of strongly diluting the reaction mixture and thus presents uncontrollable reaction conditions.